The present invention relates to a two-cycle engine, especially one in a manually-guided implement such as a power saw, a brush cutter, a cut-off machine, or the like.
U.S. Pat. No. 6,101,991 discloses a two-cycle engine having an intake duct or channel that is divided into an air channel and a mixture channel. The two-cycle engine has a carburetor in which a butterfly valve is pivotably mounted in a portion of the intake channel. In the completely opened position, the butterfly valve rests against the edge of a ring-shaped element. Downstream of the throttle shaft, a partition that divides the intake channel adjoins the ring-shaped element. Opening into the intake channel is a fuel opening that upstream of the butterfly valve is disposed at a level to which the ring-shaped element just reaches.
It has been shown that in particular in full throttle operation, in other words when the butterfly valve is disposed approximately parallel to the direction of flow in the intake channel, fuel can pass into the air channel. Due to the pulsations in the intake channel, the fuel passes into the air channel upstream of the butterfly valve. The air that is supplied to the two-cycle engine via the air channel serves to separate the fuel/air mixture in the crankcase from the exhaust gases in the combustion chamber, and to prevent fresh, non-combusted fuel/air mixture from escaping out of the combustion chamber through the outlet. The fuel that passes into the combustion chamber through the air channel can escape out of the combustion chamber with the exhaust gases, thus impairing the quality of the exhaust gas emissions.
It is an object of the present application to provide a two-cycle engine of the aforementioned general type that has lower emission values and has a straightforward construction.